3324.txt
Hewlett-Packard GmbH August 1990
HP3324A Product Note:
A multi-channel setup with programmable inter-channel phase
===========================================================
Thorough device test can rarely be done insitu. Consideration of repeatability,
limit testing, and safety -quite apart from shear feasibility- are some of the
reasons for simulating input signals rather than trying to force the real
environment to provide all desired situations at will.
Automotive, energy and navigation are example segments of the electronic
control device market where these arguments are particularly important.
Typical measurement concerns in these segments are: the relative position or
speeds of shafts, power line phase, and the computation of position from signal
phase information. In the past, the problem has been to generate a number of
synchronous signals with programmable phase difference. This product note
explains how this can be solved by master/slaving a number of HP3324A
synthesized function generators.
General description
------------------One HP3324A is equipped with Option 004 (master auto-cal) and the rest with
Option 003 (slave auto-cal). This allows the phase between channels to be set
up accurately on automatic or manual command without external phase measurement. A VHF switch (HP59307A) is required for automatic operation if more than
two channels are needed. A second switch is necessary for more than five
channels.
Features and benefits
---------------------
-No oscilloscope, phase meter or counter needed for calibration.
Auto-cal accuracy is +/-1 to +/-7 degree, depending on
waveform and amplitude mix. Refer to HP3324A data sheet.
-Manual or programmed operation.
-Extendable to virtually any number of channels.
-Output waveforms need not be the same, and are selectable from:
sine (up to 21 MHz), square or triangle (up to 11 MHz),
and ramp (up to 11 kHz). Minimum frequency is 1 mHz.
-Frequency resolution 9 digits. Stability 5ppm, can be improved
to 0.05 ppm by fitting master 3324A with Option 001.
-Independent amplitude 1 mVpp to 10 Vpp into 50 ohm. Option 002
provides 4 mVpp to 40 Vpp into 500 ohm.
Application example: control circuit for energy supply network.
------------------To test the design of a control circuit, three signals are needed to represent
the voltages of a 3-phase supply. Additionally, a signal representing current
lead or lag tests the response to power factor changes. As only one current
phase need be simulated at a time, four 3324A’s are adequate in this
application.
Setting up for the first time
----------------------------After racking or stacking the synthesizers, "daisy chain" the rear panel Reference connectors, and interconnect the Phase Cal connectors as shown in the
following diagram:
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3324.txt
Master 3324A with Option 004
______________ (and Option 001 if high stability needed)
| |
| Phase Cal In<---------------------------------------
---->Oven out (Opt)| |
| | Phase Cal Out>---------------------------- |
---->Ext.ref.in | | |
--<Ext.ref.out | | |
| |______________| | |
| | |
| | |
| 1st Slave 3324A with Option 003 |Com A |Com B
| ______________ _|__________|_
| | | | |
| | Phase Cal In<--< from A1 <--|A1 B1|--<
| | Phase Cal Out>--> to B1 <--|A2 B2|--<
-->Ext.ref.in | <--|A3 B3|--<
----<Ext.ref.out | <--|A4 B4|--<
| |______________| |______________|
| 59307A VHF switch
|
| 2nd Slave 3324A with Option 003
| ______________
| | |
| | Phase Cal In<--< from A2
| | Phase Cal Out>--> to B2
---->Ext.ref.in |
--<Ext.ref.out |
| | |
| |______________|
|
to 3rd slave, etc
Now use the following procedure to equalize the path lengths of the master
Phase Cal Output to the various slave Phase Cal Inputs:
1. Set the following parameters of all 3324As to zero:
Phase,
Assign Phase 0,
Calibration Delay, } Select Util menu and roll.
Signal Delay. }
2. Set same frequency, waveform and amplitude on all 3324As.
3. Press 1st slave’s Shift and Phase Cal keys.
4. When auto phase cal complete, measure the time interval between correspond ing points on the master and 1st slave outputs. Measure from the master
signals FORWARDS to the slave signal, even if this means nearly a full
cycle (this simplifies handling the other slaves).
5. Enter this value in ps in the 1st slave’s Calibration Delay (Util menu).
6. Do auto phase cal again, verify phase is OK.
7. Repeat steps 3 to 5 for the other slaves in turn.
Using the setup
--------------Try to use the same path lengths from the 3324A outputs to the device under
test. If this is not feasible, use a similar procedure to that above, measureing the signals at the DUT, and entering the delay into the appropriate slave’s
Signal Delay (Util menu).
From here on, correct phase relationship is simply a matter of setting each
slave to the required phase. Subsequently, whenever frequency, waveform or
amplitude are changed an auto-cal should be performed on each slave.
Start-up tools
-------------An UNSUPPORTED disk is available in order to assist implementation in an
automated environment with the following software:
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